1. Field of the Invention
The present invention relates to a portable cutting tool having a mechanism of adjusting a cutting depth of a saw blade, particularly relates to a portable cutting tool capable of fixing a cutting tool main body at a desired cutting depth position.
A cutting tool according to the invention is suitable for so-to-speak pocket cutting operation in which a workpiece is not cut from an end portion thereof but the workpiece is slit from an upper portion thereof and the workpiece is cut while maintaining a cutting depth constant. Further, the cutting tool is suitable for so-to-speak corner cutting operation for cutting a floor member along a wall side for relining the floor member of a house. A description will be given as follows by taking an example of a portable electric circular saw for convenience of explanation.
2. Description of the Related Art
An example of a portable electric circular saw of a background art is shown in FIG. 25 through FIG. 27.
In the drawings, numeral 1 designates a base, and numeral 2 designates a circular saw main body constituted to be pivotable relative to the base centering on a support shaft 9. The circular saw main body 2 includes a saw blade 3 for cutting a workpiece of a plate member or the like, and a motor (not illustrated) for driving to rotate the saw blade 3. The motor is contained in a motor housing 4 and a rotational drive force thereof is transmitted to a rotating shaft 10 of the saw blade 3 after a speed thereof is reduced by a gear contained in a gear box 7.
A saw cover 5 is attached to a cover of the gear box 7 to cover an upper portion of the saw blade 3, and a protection cover 8 is attached to a lower portion of the saw blade 3 to expose a portion of the saw blade.
As shown in FIG. 27, the base 1 is provided with an inclining mechanism 11 for inclining the main body 2 relative to the base 1. The inclining mechanism includes a support plate 12 connected to the base 1. The support plate 12 is provided with a guide hole 13 in a shape of a circular arc centering on a fulcrum of inclination, not illustrated. The base 1 can be inclined to the main body 2 by sliding a bolt 14 along the guide hole 13.
FIG. 28 shows a state of inclining the base 1 to the main body 2 by 45°. An inclinable angle is set to 45° at a maximum, and the bolt 14 is made to be able to be fixed at a desired position of the guide hole 13 such that the base 1 can be fixed at an arbitrary angular position of 0 through 45°.
On the other hand, as shown in FIG. 29, a link member 20 is connected to the base 1 for adjusting a cutting depth of the saw blade 3 for cutting a workpiece 30. The link member 20 is provided with a guide hole 22 in a shape of a circular arc centering on the support shaft 9, and a bolt 24 (FIG. 30) connecting the guide hole 22 to a lever 21 is slidably provided.
FIG. 30 is a sectional view showing to enlarge a mechanism of connecting the link member 20 and the lever 21. A thick walled portion 5a is provided at a portion of the saw cover 5 of the circular saw main body 2 and the thick walled portion 5a is provided with a hole portion formed with a female screw at an inner face thereof.
On the other hand, the bolt 24 is fixedly attached to the lever 21 by a screw 23 and the bolt 24 is constituted to screw to the hole portion provided at the thick walled portion 5a of the saw cover 5 by way of the guide hole 22 of the link member 20.
As shown in FIG. 29, the circular saw main body 2 is constituted to be able to pivot relative to the base 1 centering on the support shaft 9, and the bolt 24 is slid in the guide hole 22 of the link member 20 in accordance with pivoting movement. Therefore, the cutting depth of the saw blade 3 can freely be adjusted. Further, in order to fix the cutting depth to a desired depth, the bolt 24 is slid along the guide hole 22, the bolt 24 is moved to a desired position of the guide hole 22 and the lever 21 is pivoted. Then, by screwing the male screw and the female screw of the hole portion provided at the thick walled portion 5a of the saw cover 5, an interval between a washer 25 and a side face of the link member 20 is fastened and the circular saw main body 2 is fixed to at the position.
An explanation will be given of a method of operation when pocket cutting operation is carried out by using the electric circular saw of the background art as described above, that is, the workpiece 30 is not started to be cut from an end portion 30a (FIG. 29) thereof but the workpiece 30 is started to be cut from a middle portion 30b thereof as shown in FIG. 29.
In this case, first, the cutting depth of the saw blade 3 is fixed. That is, a position of pivoting the circular saw main body 2 relative to the base 1 is fixed by moving the bolt 24 to a desired position of the guide hole 22 of the link member 20 and turning the lever 21.
Next, in a state of exposing the saw blade by pivoting the protection cover 8 (FIG. 25) and pressing a front end portion 1a of the base 1 to fix to the workpiece 30 as shown in FIG. 29, a rear end portion 1b of the base 1 is gradually moved down to cut the workpiece 30. By cutting the workpiece 30 until the rear end portion 1b of the base 1 is brought into contact with a surface thereof and thereafter moving forward the circular saw main body 2 while bringing a lower face of the base 1 into contact with the surface of the workpiece 30, pocket cutting operation of the workpiece 30 is carried out. Also with regard to edge cutting operation, normally, similar to the pocket cutting operation, the workpiece 30 is not started to be cut from the end portion 30a (FIG. 29) but started to be cut from the middle portion 30b of the workpiece 30 as shown in FIG. 29.
There has already been known a circular saw having a structure improved for pocket cutting operation and corner cutting operation as disclosed in Japanese Patent No. 2933196, JP-A-2001-269901 and JP-A-2001-287202.